Ambient salinity and osmoregulation,energy metabolism and growth in juvenile yellowtail kingfish (Seriola lalandi Valenciennes 1833) in a recirculating aquaculture system

The effects of salinity on plasma osmolality, branchial chloride cell density, feed consumption and conversion and growth performance of yellowtail kingfish (Seriola lalandi) were evaluated. Fish (11.6 ± 0.6 g) were kept for 29 days at 14, 18, 22, 26 (experimental) and 30 g L^?1 (control) salinity in independent, pilot‐scale recirculation aquaculture systems. No differences in plasma osmolality or chloride cell numbers in gills were observed, pointing to a strong osmoregulatory capacity in the juveniles. Fish at 14, 18 and 22 g L^?1 (7.61 ± 0.19, 7.61 ± 0.01 and 7.61 ± 0.13% day^?1, respectively) had higher growth rates than fish at 26 and 30 g L^?1 (7.10 ± 0.05 and 6.97 ± 0.06% day^?1 respectively). The higher growth rate at lower salinity resulted from increased feed intake; feed conversion was not different. An evaluation of the impact of salinity on growth rate of on‐growing stages (till market size) seems warranted to assess whether the profitable effects of low salinity persist in later stages of this important aquaculture species.     

Effect of three bacterial isolates from a commercial hatchery on early red abalone (Haliotis rufescens) postlarvae

Three bacterial strains, GHrC11, GHrC13 and GHrC15, were isolated from an abalone postlarval culture system in a commercial farm at Baja California, México. The strains were phenotypically characterized and sequenced (16S rDNA). Strain GHrC11 was a Gram-positive coccobacillum, while strains GHrC13 and GHrC15 were Gram-negative bacilli. Strain GHrC11 was identified as Exiguobacterium sp. The strains GHrC13 and GHrC15 were identified as Vibrio splendidus. The effects of these strains for the development of early abalone postlarvae (2 days old) were evaluated following a completely randomized design with three replicates using 5-mL-volume Petri dishes as experimental units. The experiment considered two different bacterial concentrations of each strain (10³ and 10⁵?cells?ml^?1) and two controls (with and without the benthic diatom Navicula incerta). After 10?days of experimentation, the highest mortality (90?±?5.8?%) and the lowest growth rate (4.1?±?0.1?μm?day^?1) were recorded for the strain GHrC11. In contrast, the lower mortality (16.7?±?3.3?%) and the highest growth rate (11.2?±?0.9?μm?day^?1) corresponded to the control fed N. incerta. Our results suggest that pathogenic effects of these bacterial strains were stronger than any potential benefits derived from the ingestion of bacteria by early abalone postlarvae. In conclusion, the most pathogenic strain was GHrC11, and the intensity of pathogenicity could be ordered as Exiguobacterium sp.?>?V. splendidus (C13)?>?V. splendidus (C15).     

Development of a PCR assay for Streptococcus iniae based on the lactate oxidase (lctO) gene with potential diagnostic value

Streptococcus iniae is a well-known pathogen of both fish and humans that is difficult to identify by conventional biochemical tests. A PCR assay based on the lactate oxidase (lctO) gene of S. iniae was developed for the rapid and specific detection and identification of this pathogen from different sources. The PCR assay had a detection limit of 62-31 cells, and 25 pg of DNA per PCR reaction mixture. The PCR was also effective in detecting the bacterium from inoculated tissue homogenates, suggesting its potential use for a rapid and accurate diagnosis of S. iniae infections.     

A longitudinal study of verotoxin-producing Escherichia coli in two dairy goat herds

A longitudinal study was conducted on two dairy farms to investigate the pattern of shedding of verotoxin-producing Escherichia coli (VTEC) in goats. Faecal samples were taken from 20 goat kids once weekly during the first 4 weeks of life and then once every month for the next 5 months of life, and from 18 replacement animals and 15 adults once every month for 12 months. The proportion of samples containing VTEC was higher for replacement animals and adults (85.7% and 78.7%, respectively) than for goat kids (25.4%). About 90% of the VTEC colonies isolated from healthy goats belonged to five serogroups (O33, O76, O126, O146 and O166) but the most frequent serogroups of these isolates, except one, were different in the two herds studied. E. coli O157:H7 was found in three goat kids on only one occasion. None of the VTEC isolates, except the three E. coli O157:H7 isolates, was eae-positive. The patterns of shedding of VTEC in goat kids were variable, but, in contrast, most of the replacement animals and adults were persistent VTEC shedders. Our results show that isolates of VTEC O33, O76, O126, O146 and O166 are adapted for colonising the intestine of goats but that, in contrast, infection with VTEC O157:H7 in goats seems to be transient.     

Seasonal evolution of water status after outplanting of two provenances of Holm oak nursery seedlings

Forest restoration programs using Holm oak (Quercus ilex ssp. ballota [Desf.] Samp.) have had limited success. The effect of plant provenance on plantation success is uncertain, although some previous studies suggest that some provenances may be better able to tolerate stress. We studied the tolerance to drought in seedlings from two Spanish provenances of Holm oak before and after outplanting. One provenance was from a continental climate with cold winters (GR) and the other was from a xeric climate (HU). Seedlings were subjected to a water stress test in the nursery during the summer and survival was visually assessed after 2?weeks. In addition, 35 healthy seedlings of each provenance that were not subjected to the water stress tests were used for outplanting experiment. In these plants the seasonal changes in water potential at dawn (Ψ), specific leaf area (SLA), cuticular transpiration (E_c), and loss of xylem hydraulic conductance of twigs (PLC) were measured over 18?months. After the water stress test in summer, mortality was 44.3?% for GR seedlings and 12.6?% for HU seedlings. In addition there were differences between the two provenances in plant water status after planting. The HU provenance had a better water status and was more water conservative in the summer (higher Ψ, lower E_c, lower PLC), but not in the winter. The different drought tolerance and water relations parameters of these two provenances indicate that provenance should be considered in forest restoration and conservation programs involving Holm oak.     

Chemical composition of lignocellulosic biomass in the wood of <Emphasis Type="Italic">Abies religiosa</Emphasis> across an altitudinal gradient

Tree adaptation to environment has been extensively studied. However, little is known about the variations in structure and chemical composition of lignocellulosic biomass (LB) in relation to altitudinal gradient. We wonder, are there significant variations in the LB in the wood across an altitudinal gradient? To answer this, we carried out a study of Abies religiosa. Wood samples were collected from 36 trees, grown between 3000 and 3500 masl, and then subjected to gravimetric and FTIR (Fourier Transform Infrared) spectroscopic analyses. The gravimetric results showed a proportion of 54.81 ± 2.20 % cellulose, 12.37 ± 1.33 % hemicellulose and 24.68 ± 1.16 % of insoluble lignin. Using the principal components analysis with analysis of variance (ANOVA), significant differences were found at 3100 and 3200 masl in two independent components related to both hemicellulose and lignin, through gravimetry as well as the spectroscopic bands assigned to the carbonyl groups of these polymers, respectively. However, the observed changes in chemical composition of LB did not follow a linear relationship with respect to the altitudinal gradient, which suggests that complex environmental interactions could also be playing an important role. Also, there were significant differences (p < 0.05) in two of the empirical indexes calculated from the FTIR analysis.     

Effect of the herbicides terbuthylazine and glyphosate on photosystem II photochemistry of young olive (Olea europaea) plants

The purpose of this study was to understand the effect produced by the addition of the herbicides terbuthylazine (N(2)-tert-butyl-6-chloro-N(4)-ethyl-1,3,5-triazine-2,4-diamine) and glyphosate (N-(phosphonomethyl)glycine) on photosystem II photochemistry of young plants of Olea europaea L. under greenhouse conditions. The effect of soil amendment with an organic residue from olive oil production was also assessed. Terbuthylazine reduced the efficiency of photosystem II photochemistry of plants due to chronic photoinhibition, and this effect was counterbalanced by soil amendment with the organic waste, whereas the photosystem II photochemistry of olive plants was not affected by glyphosate or by glyphosate and organic waste addition. In this study, we have shown that the soil application of terbuthylazine is a source of indirect phytotoxicity for olive plants. We have also observed that the olive plants were not affected by higher amounts of glyphosate in the soil.     

Sediment source apportionment following wildfire in an upland commercial forest catchment

Journal of Soils and Sediments - Wildfires can have major impacts on water scarcity and water quality linked to off-site transfer of polluting ash and nutrients. Understanding sediment sources in...     

Effect of foliar salicylic acid and methyl jasmonate applications on protection against pill-bugs in lettuce plants (Lactuca sativa)

The effects were examined of plant-response signaling compounds, salicylic acid (SA) and methyl jasmonate (MeJA), on resistance to pill-bugs (Armadillidium vulgare) attack in lettuce plants. Foliar SA and MeJA applications were made at weekly intervals from the emergence of the plant until one week before harvesting. SA and MeJA induced detectable levels of hydrogen peroxide (H₂O₂) at least during 5 days post-application in these plants throughout their cultivation. On the whole, SA and MeJA in the concentrations and application scheme evaluated in this research did not significantly influence the dry and fresh weight matter of plants, or the chlorophyll and nitrate contents. In addition, both signal elicitors significantly diminished lettuce mortality due to pill-bugs, which was positively correlated with phenolics and flavonoids contents. Our results suggest that SA and MeJA, especially in low concentrations, should be further evaluated in lettuce production and priming resistance.     

Sorption of low levels of nonionic and anionic surfactants on soil: effects on sorption of triticonazole fungicide

The sorption of two anionic surfactants and a series of seven nonionic alkylphenolethoxylate surfactants of increasing hydrophilic/lipophilic balance (HLB) in a loamy clay soil was evaluated. The effect of low doses of these surfactants on the sorption characteristics of the fungicide triticonazole was investigated. The critical micellar concentration (CMC) of the surfactants in pure water and soil–water systems, and surfactant sorption were estimated by surface tension measurements using a batch equilibration technique. Triticonazole sorption, alone and in the presence of low doses of surfactants, was also measured by batch equilibration. CMC of the alkylphenol surfactants increased with their HLB. The sorption of surfactants increased with their lipophilicity. CMC in the soil–water systems were considerably higher than in pure water. Sorption of the most lipophilic alkylphenol surfactants at the higher doses significantly increased triticonazole sorption. Proposed mechanisms are modifications of soil surface properties, and increase of soil organic carbon content. Sorption of the other nonionic and anionic surfactants only resulted in monomeric surfactant concentrations in pore water, and did not affect triticonazole sorption. © 1998 Society of Chemical Industry